1. Field of the Invention
This invention relates to a support assembly for pottery articles during treatment in a kiln. The support assembly may be mounted on a kiln car and conveyed through a tunnel kiln for example.
2. Description of the Prior Art
Conventional such assemblies comprise a plurality of uprights which support shelves, the components being cemented together at every joint.
In a tunnel kiln, the kiln cars run on tracks similar to railway tracks and may bump against each other during their passage through the kiln, causing mechanical shock to be transmitted to the support assembly. Furthermore, because of the high temperatures used in kiln processes, strong thermal stresses may also occur due to expansion.
Where a support assembly for pottery articles is cemented together, there is no "play" between the components and any mechanical or thermal stress can and frequently does cause damage to the structure, which may weaken it or cause partial or total collapse with consequent damage to the pottery being treated in the kiln and possible obstruction of the kiln.
Such cemented structures also lack the ability to be readily dismantled and reassembled or altered its shape.
Other arrangements have been proposed in which the components, that is the uprights and shelves, have not been cemented together, in an attempt to avoid the above-mentioned disadvantages. If the uprights are simply used as props for the shelves, the uprights can move or tilt under mechanical or thermal stress and may leave the edges or corners of upper shelves unsupported, for example, leading to damage or possible collapse of the support assembly. To allow for this, it has proved necessary to make the props larger than would otherwise be required and this increases the ratio of the weight of the support assembly to the weight of the pottery supported thereby. This ratio, known as the "dead weight ratio", must be kept as low as possible in order to avoid the wastage of excessive amounts of heat in heating up the support assembly rather than the pottery being treated.
To reduce the instability of such arrangements, it has been proposed to use shelves having shallow blind recesses, the uprights having shallow bosses which are engageable within the recesses. In order to satisfactorily manufacture the shelves, the recesses must be relatively shallow and outwardly tapering and it is therefore impossible to interlock the components firmly. It is also necessary to make the shelves thicker than would otherwise be the case in order to provide sufficient thickness for the recesses to be incorporated and this again results in the dead weight ratio being increased.